1 /* LibTomCrypt, modular cryptographic library -- Tom St Denis 2 * 3 * LibTomCrypt is a library that provides various cryptographic 4 * algorithms in a highly modular and flexible manner. 5 * 6 * The library is free for all purposes without any express 7 * guarantee it works. 8 * 9 * Tom St Denis, tomstdenis (at) gmail.com, http://libtomcrypt.com 10 */ 11 #include "tomcrypt.h" 12 13 /** 14 @file der_decode_short_integer.c 15 ASN.1 DER, decode an integer, Tom St Denis 16 */ 17 18 19 #ifdef LTC_DER 20 21 /** 22 Read a short integer 23 @param in The DER encoded data 24 @param inlen Size of data 25 @param num [out] The integer to decode 26 @return CRYPT_OK if successful 27 */ 28 int der_decode_short_integer(const unsigned char *in, unsigned long inlen, unsigned long *num) 29 { 30 unsigned long len, x, y; 31 32 LTC_ARGCHK(num != NULL); 33 LTC_ARGCHK(in != NULL); 34 35 /* check length */ 36 if (inlen < 2) { 37 return CRYPT_INVALID_PACKET; 38 } 39 40 /* check header */ 41 x = 0; 42 if ((in[x++] & 0x1F) != 0x02) { 43 return CRYPT_INVALID_PACKET; 44 } 45 46 /* get the packet len */ 47 len = in[x++]; 48 49 if (x + len > inlen) { 50 return CRYPT_INVALID_PACKET; 51 } 52 53 /* read number */ 54 y = 0; 55 while (len--) { 56 y = (y<<8) | (unsigned long)in[x++]; 57 } 58 *num = y; 59 60 return CRYPT_OK; 61 62 } 63 64 #endif 65 66 /* $Source: /cvs/libtom/libtomcrypt/src/pk/asn1/der/short_integer/der_decode_short_integer.c,v $ */ 67 /* $Revision: 1.6 $ */ 68 /* $Date: 2006/03/31 14:15:35 $ */ 69
